666166121 has 2 divisors, whose sum is σ = 666166122. Its totient is φ = 666166120.

The previous prime is 666166069. The next prime is 666166139. The reversal of 666166121 is 121661666.

It is a strong prime.

It can be written as a sum of positive squares in only one way, i.e., 599515225 + 66650896 = 24485^2 + 8164^2 .

It is a cyclic number.

It is not a de Polignac number, because 666166121 - 2²⁶ = 599057257 is a prime.

It is not a weakly prime, because it can be changed into another prime (666166141) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (17) of ones.

It is a polite number, since it can be written as a sum of consecutive naturals, namely, 333083060 + 333083061.

It is an arithmetic number, because the mean of its divisors is an integer number (333083061).

Almost surely, 2^666166121 is an apocalyptic number.

It is an amenable number.

666166121 is a deficient number, since it is larger than the sum of its proper divisors (1).

666166121 is an equidigital number, since it uses as much as digits as its factorization.

666166121 is an odious number, because the sum of its binary digits is odd.

The product of its digits is 15552, while the sum is 35.

The square root of 666166121 is about 25810.1941294520. The cubic root of 666166121 is about 873.3617765374.

The spelling of 666166121 in words is "six hundred sixty-six million, one hundred sixty-six thousand, one hundred twenty-one".